Pin joints for machinery generally fall into two categories. Dynamic joints where structural members move relative to each other and static joints where the structural members do not move. When dynamic joints are present, they may move back and forth making oscillatory motion. As can be imagined, this creates friction and wear that may limit the life of the pin joint. Consequently, the art has developed schemes to limit this friction and prolong the life of the pin joint.
Oscillating pin joints in construction and mining equipment typically include a pin and a mating bearing that is press fit into the surrounding structure. The pin is typically heat treated to provide the material strength needed to carry working loads and also to provide a hard outer diameter surface for improved wear and galling resistance. The pin is often plated to improve wear and corrosion resistance, especially in the un-lubricated “static” bores that support each end of the pin. For most common bearing materials, the pin to bearing interface must be periodically lubricated in order to provide suitable performance and durability.
In such applications, grease lip seals that comprise a steel can or backbone that supports a single urethane lip to protect the pin-to-bearing interface have been developed. However, these seals are not designed for performance and long life in the absence of a lubricant so routine maintenance is vital to maintaining the longevity of the joint.
As can be imagined, the heat treatment and plating operations increase the initial cost of the pin joint, and the need for periodic lubrication reduces machine availability and increases owning and operating cost. Therefore, it is desirable to develop a dynamic pin joint for machinery that is less costly or more robust than has yet been devised.